Conventionally, there are various radar devices for detecting an object within a detection area by transmitting electromagnetic wave signals to the detection area. The radar devices form a detection image of the detection area by receiving echo signals which are caused by the transmitted electromagnetic wave signals reflecting on the object. Then, the radar devices display the formed detection image on a display module. Thus, a user can visually recognize the object within the detection area by viewing the detection image. When this kind of radar device is carried on a ship to detect objects around the ship, the radar device receives echo signals reflected on various objects, such as land, birds, other ships, banks, and/or buoys, as well as receives noise signals. For this reason, the user may suffer difficulties in distinguishing whether displayed echoes are object or noise.
JP3794361B2 discloses an atmospheric observation radar signal processing device which removes abnormal echo signals due to birds passing through the sky above the device while accurately performing atmospheric observation using wind velocity instruments etc. . . . The device particularly removes the abnormal echo signals reflected on birds without removing necessary echo signals reflected on geographical features which can be identified comparatively easily. Thereby, the user can acquire information only related to atmospheric observation.
However, when removing echo signals that are not easily identifiable, the conventional device may also remove echo signals reflected on objects for which the user needs information.